Chemical treatment to retard diffusion in a semiconductor overlayer

Abstract

The present invention provides a method for retarding the diffusion of dopants from a first material layer (typically a semiconductor) into an overlayer or vice versa. In the method of the present invention, diffusion of dopants from the first semiconductor into the overlayer or vice versa is retarded by forming a monolayer comprising carbon and oxygen between the two layers. The monolayer is formed in the present invention utilizing a chemical pretreatment process in which a solution including iodine and an alcohol such as methanol is employed.

1. A method of controlling dopant diffusion comprising:
 forming a monolayer comprising carbon and oxygen on a first semiconductor layer that includes dopants therein, said monolayer substantially retards diffusion of dopants; 
 annealing said first semiconductor layer and said monolayer to activate said dopants; and 
 forming a second semiconductor layer on said monolayer. 
 
   
   
     2. The method of  claim 1  wherein said first semiconductor layer is subjected to a step in which a surface native oxide layer is removed prior to forming said monolayer. 
   
   
     3. The method of  claim 2  wherein said surface native oxide layer is removed by a hydrofluoric acid-containing solution. 
   
   
     4. The method of  claim 1  wherein said first semiconductor layer is subjected to a hydrogen termination processing step prior to forming said monolayer. 
   
   
     5. The method of  claim 4  wherein said hydrogen termination processing step comprises contacting the first semiconductor layer with hydrofluoric acid either in solution or in the gas phase. 
   
   
     6. The method of  claim 4  wherein said hydrogen termination processing step comprises a hydrogen anneal. 
   
   
     7. The method of  claim 1  wherein said dopants are n-type dopants or p-type dopants. 
   
   
     8. The method of  claim 1  wherein said second semiconductor layer is doped. 
   
   
     9. The method of  claim 1  wherein said forming said monolayer comprises contacting the first semiconductor layer with a solution comprising iodine and an alcohol. 
   
   
     10. The method of  claim 9  wherein said solution comprising iodine and an alcohol contains from about 1×10 −3  to about 1×10 −5  M of iodine in alcohol. 
   
   
     11. The method of  claim 9  wherein said alcohol comprises methanol. 
   
   
     12. The method of  claim 1  wherein said forming a second semiconductor layer comprises a deposition process that is performed at a temperature of about 500° C. or greater. 
   
   
     13. A method of controlling dopant diffusion comprising:
 forming a monolayer comprising carbon and oxygen on a first material layer; and 
 forming an overlayer on said monolayer, wherein one of said first material layer or said overlayer contains dopants and said monolayer substantially retards diffusion of said dopants; and 
 annealing said first material layer, said monolayer and said overlayer. 
 
   
   
     14. The method of  claim 13  wherein said first material layer is a first semiconductor layer which is subjected to a step in which a surface native oxide layer is removed prior to forming said monolayer. 
   
   
     15. The method of  claim 13  wherein said first material layer is subjected to a hydrogen termination processing step prior to forming said monolayer. 
   
   
     16. The method of  claim 15  wherein said hydrogen termination processing step comprises contacting the first material layer with a hydrofluoric acid-containing solution, a gas phase containing hydrofluoric acid or a hydrogen anneal. 
   
   
     17. The method of  claim 13  wherein said dopants are n-type dopants or p-type dopants. 
   
   
     18. The method of  claim 13  wherein said dopants are located in said first material layer. 
   
   
     19. The method of  claim 13  wherein said dopants are located in said overlayer. 
   
   
     20. The method of  claim 19  wherein said alcohol comprises methanol. 
   
   
     21. The method of  claim 13  wherein said forming said monolayer comprises contacting the first material layer with a solution comprising iodine and an alcohol. 
   
   
     22. The method of  claim 21  wherein said solution comprising iodine and an alcohol contains from about 1×10 −3  to about 1×10 −5  M of iodine in alcohol. 
   
   
     23. The method of  claim 13  wherein said overlayer comprises a semiconductor material, an insulator, a conductor or any combination thereof. 
   
   
     24. The method of  claim 13  wherein said forming the overlayer comprises a deposition process that is performed at a temperature of about 500° C. or greater. 
   
   
     25. The method of  claim 13  wherein said first material layer comprises an insulator and the overlayer comprises a conductor.